Most of the body of knowledge that has been built up over the years regarding the functionality of lipids in food systems has been based on experiments designed around variations of naturally occurring fats and oils. The functional performance of these fats, from whatever source, was related to specific analytical characteristics that still enjoy wide use in the industry, i.e., Solid Fat Index, Iodine Value, and Fatty Acid Composition. In addition to these characteristic values, a number of analytical tests were routinely performed on the fats that were indicators of its quality, or its ability to withstand the stresses of temperature and shelf-life requirements. These included free fatty acid content, peroxide value, color, odor, etc. None of these tests, however, related the functional performance of the fat to the presence (or absence) of any specific triglyceride having a specific structure, i.e., which fatty acid was on which carbon of the glycerol backbone. In the majority of cases, however, such knowledge would have been of academic interest only since the availability of such structured fats in any great proportion within a given fat system were simply not available. Aside from cocoa butter and some of the other more exotic tropical fats, most fats used in foods consist of a random assortment of triglycerides driven by the types and levels of fatty acids that make up their composition, so that such knowledge would have no direct bearing on a formulator's capabilities.
Cocoa butter makes up approximately one third of chocolate's content, and it is responsible for the much-appreciated characteristics of chocolate. Such characteristics include chocolate's hardness and brittleness at ambient temperatures, quick and complete melting in the mouth, gloss, shelf life, aroma and taste.
It is believed that the carbon chain length of the fatty acids making up cocoa butter as well as the symmetry of the acids positioned on the glycerol moiety are responsible for the much-appreciated characteristics. In fact, three fatty acids completely dominate the composition of cocoa butter: palmitic acid, stearic acid and oleic acid. Practically all oleic acids occur esterified in position two of glycerol, with two fully saturated fatty acids, stearic and palmitic acids, occupying the two remaining positions--positions one and three. As reported in Cocoa Butter Alternatives, Karlshamns Oils & Fats Academy, page 9, .COPYRGT. 1991 (herein incorporated by reference), this gives rise to three completely dominant symmetrical triglycerides, POP (palmitate, oleate, palmitate), POST (palmitate, oleate, stearate) and STOST (stearate, oleate, stearate), that resemble each other closely and make up almost 80% of cocoa butter. Because of this symmetry, cocoa butter is deemed a symmetrical triglyceride. However, because cocoa butter is expensive, and its supply is limited, various researchers have spent considerable amounts of time in developing fats that could serve as alternatives to cocoa butter by providing similar properties to its melting profile and solids content at various temperatures. Several classes of alternatives have been developed, ranging from cocoa butter "equivalents" produced from selected blends of fractions of natural fats that are high in specific triglyceride contents, and which are miscible in all proportions to cocoa butter, to the use of fats containing totally different triglyceride distributions, but which mimic, in many ways, the melting behavior of cocoa butter. An example of the production of a cocoa butter "equivalent" would involve the purification and frationation of a series of different naturally occurring fats to obtain the proper proportion of the desired triglycerides having the desired structure, at the appropriate levels. Commonly used sources of these specialty fats and their triglyceride distributions are given in the table below. The majority of the POP portion required is obtained from palm mid-fraction.
______________________________________ Triglyceride Composition of Sal, Kokum, Shea and Illipe Fats (% by weight) Triglyceride Sal Kokum Shea Illipe ______________________________________ POO 3 -- 2 -- POSt 11 5 5 35 StOSt 42 72 40 45 StOO 16 15 27 3 StOL 1 -- 6 -- StOA 13 -- 2 4 OOO 3 2 5 -- POP 1 0 0 7 Others 10 6 13 6 ______________________________________
Recently, a great deal more effort has been expended against the study of structured triglycerides in foods, and these have led to the market introduction of synthesized species that have been almost exclusively targeted at the confectionery market for the replacement of cocoa butter, with the additional benefit of producing reduced calorie products. These products take advantage of the effects of positional isomerism on the glycerin backbone to address the specific physical properties required in the final food product, plus utilize the differences in caloric contribution of the various fatty acids used to arrive at a lowered calorie intake. The drawback of these novel ingredients is that they are costly to manufacture, and require a series of synthetic steps along with requisite purification procedures. The final price to the end-user is still several dollars per pound. At this price, their ultimate use is restricted to specific niche markets within the food industry rather than being able to effect a significant move towards their use in a wide array of food products.
The assignee of the present application has developed genetically engineered annual plants that will selectively produce laurate canola oil. These plants are described in U.S. Pat. No. 5,344,771, herein incorporated by reference.
In laurate canola oil, two fully saturated fatty acids of equal length occupy positions one and three of the glycerol moiety in a majority of instances, and a C18 fatty acid occupies position two of the glycerol moiety in substantially all instances. The symmetry in the engineered triglyceride is not as prevalent as found in cocoa butter, and for this reason, the triglycerides of the invention are deemed structured triglycerides. In essence, the preferred and dominant occurring structured laurate canola oil looks like this: ##STR1## wherein X in the C18 fatty acid is 0, 1, 2 and 3, or the C18 fatty acid may be partially hydrogenated. Hydrogenation will allow for variation in the Solid Fat Index profiles of resulting fats.
The assignee has also produced a structured stearate oil, wherein, again, fully saturated fatty acids of a carbon length of eighteen carbon atoms occupy positions one and three of the glycerol moiety a majority of the time and a C18 fatty acid is found at position two substantially all of the time which may be or may not be partially hydrogenated. Such a structured lipid is described in International Patent Application No. PCT/US91/01746, herein incorporated by reference.
The assignee has now found that substitution of the structured lipids for conventional shortening compositions in food products enhances a host of characteristics of such products.